The present invention relates to a method for preventing feedback between co-resident or collocated teleconferencing endpoints.
Teleconferencing involves several occupants at several different sites who participate in a conference through teleconferencing endpoints arranged at each location. At each site, a teleconference endpoint, typically a speakerphone, is communication with a conference bridge which adds or mixes the audio signals transmitted from each location such that all participants hear one another while insuring that no site receives a mix containing audio transmitted from its own speakerphone.
If one of the sites is a large conference room with many participants, it may be advantageous to use more than one speakerphone so that each of the participants is nearer to a microphone and is closer to a transmitting loudspeaker for ease of listening. However, the connection of two or more speakerphones located in the same acoustic space (i.e., the same room) to the same conference bridge sets up an audio feedback path that can induce howling or feedback. For example, if two speakerphones A and B are used in the same room, the speech transmitted from the microphone of speakerphone A is sent to the conference bridge, where it is mixed with the audio stream from other participating speakerphones and transmitted to the loudspeaker of speakerphone B. Thus, a feedback loop exists from speakerphone A to speakerphone B and vice versa. Such feedback would, incidentally, produce an annoying echo since the loop through most conference bridges produces a perceptible delay. This feedback problem occurs because the bridge is not aware that the speakerphones A and B are co-resident or collocated teleconferencing endpoints.